This invention comprises an actuator for remote operation of a circuit breaker, such as a recloser-type circuit breaker, in a power distribution network.
Circuit breakers are typically provided in power distribution networks to detect when a fault occurs and disconnect power from a section of the line to ensure the safe operation of the distribution system. One type of sectionaliser circuit breaker is known as a recloser. A recloser is configured to disconnect power to a distribution line or lines if it detects the occurrence of a fault. A recloser will normally break the power supply circuit if it detects a fault and then reconnect the circuit again after a short delay. If the fault is still present, the recloser will again disconnect the supply circuit and then reconnect it after another delay period. If the fault is still present on the line after the second reconnection, this will trigger the recloser into again disconnecting the power supply circuit and a manual override switch on the recloser will be disengaged. Once the manual override switch has disengaged (which in commonly used forms of recloser is indicated at the exterior of the recloser by a flag or lever being dropped downwards) the power distribution circuit cannot be reconnected until the manual override switch is physically moved into its engaged position by a technician or linesman.
Most reclosers also include a manually actuated non-reclose lever. If this lever is operated by a linesman or technician the manual override lever will automatically disengage the first time a fault is detected on a power distribution line. This non-reclose lever is used when a technician or linesman is trying to determine the location of a fault and does not wish the recloser to automatically reconnect the power after a short delay.
U.S. Pat. No. 5,641,059 describes an actuator which is coupled to a recloser and which can be controlled over a radio link to enable remote operation of the recloser. This remotely controlled actuator comprises driving motors to drive an actuator arm that operates the manual controls of the recloser, to eliminate the need for a technician to travel out to the site of the actuator. However, in this form of remote control actuator an actuator arm is driven upwards and downwards by a direct link to an electric motor and it has been found that if the electric motor or its controlling circuitry fails, it is possible that the motor will drive the actuator arm up to a position where it will permanently jam on the manual override lever of the recloser. This situation is referred to as the recloser lever being xe2x80x9chung upxe2x80x9d. The effect can be that the recloser cannot operate as normal and shut off or break the power supply to the line in the event of a fault. This may result in the recloser exploding, damage to the power distribution line, or even a blackout.
In broad terms in one aspect the invention comprises an actuator for remote operation of a switch, comprising an electric mechanism which is energisable to mechanically operate the switch on command and which is otherwise mechanically disengaged from the switch such that the switch may operate freely, and a receiver arranged to receive remotely transmitted command signals for the electric mechanism.
In broad terms in a further aspect the invention comprises an actuator for remote operation of a circuit breaker, comprising an electric motor and an electro-magnetic clutch mechanism which is energisable to connect the motor drive to mechanically operate the circuit breaker and which is otherwise disengaged such that the circuit breaker may operate freely, and a receiver arranged to receive remotely transmitted control signals and control operation of the electric motor and electro-magnetic clutch to operate the actuator.
In one preferred form the invention comprises an actuator for remote operation of a recloser-type circuit breaker comprising manual override and non-reclose controls, comprising one electro-magnetic clutch mechanism energisable to connect a mechanical drive to operate the manual override control and which is otherwise disengaged such that the manual override control may move freely, a second electro-magnetic clutch mechanism energisable to connect a mechanical drive to operate the non-reclose control and which is otherwise disengaged such that the non-reclose control may move freely, and a receiver arranged to receive remotely transmitted control signals and control operation of the mechanical drive and electro-magnetic clutch mechanisms to enable remote operation of the circuit breaker.
The actuator of the invention is particularly intended for use with pole-top mounted recloser-type electrical circuit breakers but may be used with any other form of circuit breaker which term should be understood as arranged to interrupt or reconnect the supply of electrical power in a power distribution network including for example ring main units, gas switches, air brake switches, or similar.
The actuator may be a separate unit which is adapted to be retro-fitted to existing circuit breakers such as pole-top recloser-type circuit breakers in a power distribution network, and in particular be coupled to the manual override and non-reclose controls of an existing recloser for example, or may alternatively be incorporated as an integral part of original equipment remotely operable circuit breaker.